Showing papers in "Materials Transactions in 2007"

Theory of Shear Banding in Metallic Glasses and Molecular Dynamics Calculations

Abstract: The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses (Acta Mater. 54 (2006) 4293), based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis. The model predicts the existence of a critical lengthscale � 10 nm, above which melting could occur in shear-alienated glass. Large-scale molecular dynamics simulations with up to 5 million atoms have directly verified this prediction. When the applied stress exceeds the glue traction (computed separately before in a shear cohesive zone, or an amorphous-amorphous ‘‘generalized stacking fault energy’’ calculation), we indeed observe maturation of the shear band embryo into bona fide shear crack, accompanied by melting. In contrast, when the applied stress is below the glue traction, the shear band embryo does not propagate, becomes diffuse, and eventually dies. Thus this all-important quantity, the glue traction which is a property of shearalienated glass, controls the macroscopic yield point of well-aged glass. We further suggest that the disruption of chemical short-range order (‘‘chemical softening’’) governs the glue traction microscopically. Catastrophic thermal softening occurs only after chemical alienation and softening in our simulation, after the shear band embryo has already run a critical length. [doi:10.2320/matertrans.MJ200769]

Formation and Mechanical Properties of Mg97Zn1RE2 Alloys with Long-Period Stacking Ordered Structure

Abstract: We investigated the formation and mechanical properties of Mg 97 Zn 1 RE 2 alloys with long-period stacking ordered (LPSO) structures by examining RE = Y, La, Ce, Pr, Sm, Nd, Gd, Dy, Ho, Er, Tb, Tm and Yb The LPSO phase developed for RE = Y, Dy, Ho, Er, Gd, Tb and Tm LPSO Mg-Zn-RE alloys are either type I, in which the LPSO phase forms during solidification: Mg-Zn-Y, Mg-Zn-Dy, Mg-Zn-Ho, Mg-Zn-Er and Mg-Zn-Tm, or type II, in which the LPSO phase is nonexistent in as-cast ingots but precipitates with soaking at 773 K: Mg-Zn-Gd and Mg-Zn-Tb The criteria for REs that form an LPSO phase in Mg-Zn-RE alloys are discussed Mg-Zn-RE alloys with an LPSO phase, which were worked by hot extrusion, include high strength both at ambient and elevated temperatures, and good ductility Their tensile yield strength, ultimate strength and elongation were 342-377 MPa, 372-410MPa and 3-9%, respectively at ambient temperature, and 292-310MPa, 322-345 MPa and 4-13% at 473 K The LPSO Mg-Zn-RE alloys are promising candidates for lightweight structural materials

Effect of Annealing on the Interfacial Structure of Aluminum-Copper Joints

Abstract: The aim of this study is to investigate the structure development and growth kinetics of the interfacial structure of cold roll bonded Al/Cu bimetal sheet. An interfacial structure is developed during the annealing process. The characteristics of the constituent phases at the interface of Al/Cu bimetal are studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results indicate that an obvious multi-layers interdiffusion structure is developed at the Al/Cu interface. The diffusion layer is consisted of four intermetallic compounds; Al 2 Cu, AlCu, Al 3 Cu 4 and Al 4 Cu 9 . The growth of these intermetallics during annealing can be achieved by the diffusion process. The activation energies of Al 2 Cu, AlCu + Al 3 Cu 4 , Al 4 Cu 9 and the total intermetallic layer are found to be 97.504, 107.46, 117.52 and 107.85kJ/mol, respectively. These intermetallics generally possess higher hardness values than those of the corresponding base metals. AlCu and Al 3 Cu 4 exhibit much higher hardness than that of Al 2 Cu and Al 4 Cu 9 , which implies lower fracture toughness. The observation of crack propagation paths shows that fracture mainly occurs in the intermetallic compound layers of AlCu and Al 3 Cu 4 , which are located between Al 2 Cu and Al 4 Cu 9 .

High Thermal Conductivity of Gallium Nitride (GaN) Crystals Grown by HVPE Process

Abstract: A relatively large sample of gallium nitride (GaN) was grown as a single crystal using the hydride vapor phase epitaxy (HVPE) process. The thermal diffusivity of the single crystal has been measured using a vertical-type laser flash method. The thermal expansion was measured using a dilatometer in order to estimate the thermal diffusivity with sufficient reliability. The effect of sample thickness and temperature on thermal diffusivity was evaluated. The specific heat capacity of GaN was also measured by using a differential scanning calorimeter. The thermal properties of single-crystal GaN have been compared with the measured thermal properties of single-crystal silicon carbide (SiC). The thermal conductivity of single-crystal GaN at room temperature is found to be 253 � 8:8% W/mK, which is approximately 60% of the value obtained for SiC. The excellent thermal property that is obtained in this study clearly indicates that GaN crystals are one of the promising materials for use in high-power-switching devices. [doi:10.2320/matertrans.MRP2007109]

Effects of Transmutation Elements on Neutron Irradiation Hardening of Tungsten

Abstract: Tungsten (W) is a candidate material for Plasma facing materials of fusion reactors. During fusion reactor operation, not only irradiation damages but also transmutation elements such as rhenium (Re) and osmium (Os) are produced by neutron irradiation. As a result, the original pure tungsten changes to W-Re or W-Re-Os alloys. Thus, the mechanical and physical properties are expected to change. The aim of this study is to investigate the effects of transmutation elements on neutron irradiation hardening and microstructure changes of tungsten. To simulate the effects of transmutation elements, tungsten base model alloys were used in this study. The examined compositions of the alloys were selected from the calculated changes in solid solution area of W-Re-Os alloy. Neutron irradiation was performed in fast test reactor JOYO in JAEA. The irradiation damages and temperature ranges were 0.17–1.54 dpa and 400–750 � C respectively. After the irradiation, Vickers hardness test and TEM observation were performed. There were clear differences between Re and Os in effects on irradiation hardening. In the case of W-Re alloys, when damages were less than 0.40 dpa, the irradiation hardenings were nearly equal to those of pure tungsten independent of Re addition. But when the damage was 1.54 dpa, the irradiation hardenings increased lineally with Re content. Microstructural observations showed that precipitations mainly formed in W-Re alloys. In the case of W-Os alloys, the irradiation hardenings (� Hv) of W-3Os alloys were larger than those of pure tungsten. And the differences were about 400 independent of dpa and irradiation temperature. Effects of Re and Os on irradiation hardening based on the microstructural observations were discussed. [doi:10.2320/matertrans.MAW200722]

Structural Changes of Precipitates in an Mg-5 at%Gd Alloy Studied by Transmission Electron Microscopy

Abstract: Structural changes of precipitates in an Mg-5 at%Gd (Mg 95 Gd 5 ) alloy by aging at 200°C and 250°C have been studied by ordinary high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). In the early stage of precipitation by aging at 200°C up to 5 h, a short-range ordered structure exists in Gd-enriched regions with an about 2 nm size, and nuclei of an Mg 7 Gd structure (β' phase) occur in the short-range ordered structure by aging at 200°C for 5 h. The β' phase with the Mg 7 Gd structure is formed as definite precipitates by aging at 200°C for 10 h. The β' precipitates are joined along the b-axis and form a plate-shape with a thickness of about 20 nm along the a-axis, and lengths of about 200 nm along the b-axis and 200 nm along the c-axis, and the connection of planar precipitates along the three directions, which are parallel to the [210] m ,-typed directions of the Mg-matrix, forms a two-dimensional cell structure, by top-aging at 200°C for 100h.

Thermal Properties and Phase Stability of Zn-Sn and Zn-In Alloys as High Temperature Lead-Free Solder

Abstract: The potential of newly-designed Zn-xSn (x ¼ 40, 30, and 20 mass%) and Zn-30 mass%In alloys as high temperature lead-free solders was evaluated, with particular focus on the fundamental thermal properties and phase stability during thermal and humidity exposure. From DSC results, the melting temperature of Zn-Sn alloys increased with decreasing Sn content, and the final undercooling was about 3 � C. The liquid fraction of the alloys calculated using Scheil’s model is lower than that of the alloys calculated according to the phase diagram by approximately 10 mass% at the eutectic temperature and 250 � C. The coefficients of thermal expansion (CTE) of Zn-Sn alloys increased with decreasing Sn content, i.e. 29:2 � 10 � 6 � K � 1 to 33:2 � 10 � 6 � K � 1 in the temperature range of � 50 � C to 200 � C for Zn-Sn alloys and 31:3 � 10 � 6 � K � 1 in the temperature range of � 50 � C to 140 � C for Zn-30In alloy. With increasing temperature above eutectic temperature, all alloys began to deform, indicating the formation of a liquid phase. The thermal deformation of Zn-Sn alloys decreased with increasing Sn content. The ultimate tensile strength (UTS) and 0.2% proof stress of the as-cast Zn-Sn alloys were almost the same, but the elongation of the as-cast Zn-Sn alloys decreased with increasing Sn content. After thermal and humidity exposure for 1000 h (85 � C/85% Relative Humidity), only the outer surface of Zn-Sn alloys oxidized. However, Zn-30In alloy rusted quite seriously resulting in Zn oxidation after 1000 h. The UTS and 0.2% proof stress of Zn-Sn alloy slightly decreased with increasing exposure time. The elongation of Zn-Sn alloys decreased with decreasing Sn content for 100 h exposure. However, the elongation of Zn-Sn alloys showed no further degradation beyond 100 h exposure. [doi:10.2320/matertrans.48.584]

Ductile Fe-Based Bulk Metallic Glass with Good Soft-Magnetic Properties

Abstract: We report a ductile Fe-Mo-P-C-B bulk metallic glass (BMG) with good soft-magnetic properties. The Fe-Mo-P-C-B BMG with high Poisson's ratio of 0.325 and low glass transition temperature of 708 K exhibits plastic strain up to 5.5% before final failure and high fracture strength of 3280 MPa in compression. The Fe-based BMG possesses high saturation magnetization of 1.1 T, low coercive force of 1.8 Am � 1 and high permeability of 55300. The Fe-Mo-P-C-B BMG with this combination of noticeable ductility, high strength and good soft-magnetic properties previously not observed simultaneously in Fe-based glassy alloys has promising potential in functional and structural applications. (doi:10.2320/matertrans.48.1157) duction melting mixtures of pure Fe (99.9 mass%), Mo (99.9 mass%), C (99.9 mass%) and B (99.9 mass%), and pre- alloyed Fe-P with known analyzed composition under a high- purity argon atmosphere. From the master alloy, ribbons were prepared by melt-spinning, and cylindrical rod and ring- shaped samples were prepared by copper mold casting under an argon atmosphere. The structure of the specimens was examined by X-ray diffracometry (XRD) with Cu-K� radiation and transmission electron microscopy (TEM). Glass transition, crystallization and melting behaviors of the glassy samples were evaluated by differential scanning calorimetry (DSC) at a heating rate of 0.33 K/s. Compressive deformation tests were performed on a material test system (MTS) at a strain rate of 2:1 � 10 � 4 s � 1 at room temperature using glassy rods with a dimension of 1 mm in diameter and 2 mm in length. Samples subjected to compressive tests were observed by scanning electron microscopy (SEM). Ultra- sound measurements were carried out to determine the elastic constants and the Poisson's ratio of the BMG. Saturation magnetization (Bs) was measured by a vibrating sample magnetometer (VSM) with a glassy rod of 1 mm in diameter. Coercive force (Hc) and DC permeability (� DC) were evaluated by a DC B-H loop tracer using the glassy ring- shaped samples. Structure and magnetic properties of the bulk glassy specimens annealed at a temperature of (Tg � 50) K( Tg is glass transition temperature) for 10 minutes were also examined. 3. Results and Discussion

FeSiBP Bulk Metallic Glasses with Unusual Combination of High Magnetization and High Glass-Forming Ability

Abstract: Among many kinds of bulk metallic glasses (BMGs), Fe-based BMGs with good magnetic properties, high strength and low materials cost should have great potential for wide variety of applications. However, the glass-forming metal elements such as Al, Ga, Nb, Mo, Y and so forth in the Fe-based BMGs significantly decrease saturation magnetization (Js) which is a essential property as soft magnetic materials and also increase the material cost. The coexistence of high Fe content and high glass-forming ability (GFA) has been earnestly desired from academia to industry. We report a novel Fe76Si9B10P5 (at%) bulk metallic glass with unusual combination of high J s of 1.51 T due to high Fe content and high GFA leading to a glassy rod with a diameter of 2.5 mm despite not-containing any glass-forming metal elements. This alloy composed of familiar and low-priced elements, also exhibiting very excellent magnetic softness and rather high strength, has a great advantage for engineering and industry, and thus should make a contribution to conservation of earth resources and environment through energy saving. [doi:10.2320/matertrans.MRP2007198]

Computation of Interfacial Thermal Resistance by Phonon Diffuse Mismatch Model

Abstract: The thermal resistances of 1250 kinds of interface were computed at room temperature based on the phonon diffuse mismatch model. The result shows that the ratio of Debye temperature and the ratio of average sound velocity can be approximately used to characterize the difference of two materials in terms of interfacial thermal resistance. The high interfacial thermal resistances are composed of high and low Debye temperature materials. The low interfacial thermal resistances are composed of both similar Debye temperature materials, and their Debye temperatures are very high. The relation between the interfacial thermal resistance with the ratio of average sound velocity is similar to that of the ratio of Debye temperature. [doi:10.2320/matertrans.MAW200717]

Characterization of β' Precipitate Phase in Mg-2 at%Y Alloy Aged to Peak Hardness Condition by High-Angle Annular Detector Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM)

Abstract: Theβ' phase precipitated in an Mg-2 at%Y (Mg 98 Y 2 ) alloy aged to a peak hardness condition at 200°C for 336 h has been studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The β' precipitates have an about 20 nm size and definite facets parallel to the (010) plane, and Y-enriched double atom planes parallel to the (010) plane grow long and sometimes individually along the [100] and [001] directions. This morphology of the β' precipitates in the Mg 98 Y 2 alloy is remarkably different from that in an Mg 95 Gd 5 alloy.

Mechanical properties of co-based L12 intermetallic compound Co3(Al,W)

Abstract: Mechanical properties of L1 2 -Co 3 (A1,W) polycrystalline sample are investigated by compression testing at various temperature ranging from room temperature to 1193 K. It was found that at room temperature the 0.2% flow stress is 410 MPa and the compressive ductility is higher than 10%, whereas at 1193K the 0.2% flow stress is 382 MPa and the compressive ductility is about 10%. Two candidates for the reaction scheme of the Co-rich region of the Co-Al-W ternary phase diagram are proposed by combining the results of microstructure observation, X-ray diffractometry and the previous report.

Preparation of Cu36Zr48Ag8Al8 Bulk Metallic Glass with a Diameter of 25 mm by Copper Mold Casting

Abstract: The Cu 36 Zr 48 Ag 8 Al 8 alloy exhibits very high glass-forming ability. We have succeeded in synthesizing a Cu 36 Zr 48 Ag 8 Al 8 bulk glassy alloy with a diameter of 25 mm using the conventional copper mold injection casting. The absence of a crystalline phase was confirmed by X-ray diffraction and differential scanning calorimetry examinations. The critical cooling rate for formation of a glassy phase for the Cu 36 Zr 4 Ag 8 Al 8 alloy was estimated to be less than 6.4 K/s. High glass-forming ability and high strength might contribute to its commercial application for the Cu 36 Zr 48 Ag 8 Al 8 bulk metallic glass.

Texture Control for Improving Deep Drawability in Rolled and Annealed Aluminum Alloy Sheets

Abstract: In order to find a possibility of texture control for improving deep drawability in rolled and annealed aluminum alloys, the relation among recrystallization texture, r-value and limiting drawing ratio was examined for sheet materials with various textures. By using specimens with {111} texture prepared artificially, limiting drawing ratio could be measured in a wide range of average r-value from 0.4 to 1.6. Experimental results demonstrated that there was a positive correlation between average r-value and limiting drawing ratio even in aluminum alloys. This means that an increase in average r-value leads to improvement of deep drawability. Warm rolling that forms shear texture including {111} components, therefore, was conducted to enhance average r-value for Al-Mg and Al-Mg-Si alloys. Recrystallization texture of an annealed Al-Mg alloy consisted of retained shear texture components in the surface layer and cube plus R orientations in the center layer. The average r-value was considerably improved compared with that of a cold rolled sheet. On the other hand, a T4-treated Al-Mg-Si alloy had a relatively weak cube texture on the whole, though the surface layer showed a different texture from the center. In this case, warm rolling was ineffective in improving average r-value, in spite of the existence of surface texture with higher r-value. However, the relation between recrystallization texture and experimental r-value was successfully explained for the Al-Mg-Si alloy as well as for the Al-Mg alloy, based on r-value calculations from overall texture through sheet thickness.

Dynamic Substance Flow Analysis of Aluminum and Its Alloying Elements

Abstract: Aluminum demand in Japan has grown significantly during the last few decades. For most uses, small amounts of other metals are added to the primary aluminum to make harder alloys, which are classified by the nature and concentrations of their alloying elements. Aluminum scraps from end-of-life products, which are used as raw materials for secondary aluminum, are often mixtures of several alloys. Therefore, not only the amount of scrap but also the concentrations of their alloying elements must be taken into account when assessing the maximum recycle rate of aluminum scraps. This paper reports a dynamic substance flow analysis of aluminum and its alloying elements in Japan, focusing on the alloying elements Si, Fe, Cu and Mn. We devised eight categories of aluminum end uses and 16 types of aluminum alloys. The amount of each alloy in each end-use category was estimated from statistical data. We then estimated future quantities of discarded aluminum in each of the eight categories using the population balance model. At the same time, we calculated the concentrations of the alloying elements in each of the end uses. It was estimated that the amount of aluminum recovered in Japan would be about 1800 kt in 2050, which is 2.12 times that recovered in 1990. Calculated concentrations of alloying elements in aluminum scraps showed good correlation with those of the measured data. [doi:10.2320/matertrans.MRA2007102]

Acquisition and Analysis of Continuous Acoustic Emission Waveform for Classification of Damage Sources in Ceramic Fiber Mat

Abstract: Waveforms of acoustic emission (AE) events come close and sometimes overlap each other when AE activity is very high. Conventional AE measurement systems which handle discrete AE events are not suitable for this situation because miss-detection of AE event occurs frequently. A new AE measurement system named as Continuous Wave Memory (CWM) was developed to solve this problem by recording the AE waveforms continuously to hard disks for several hours throughout the testing time. This new system enabled multiple analysis of one waveform with different filtering parameters. Short time Fourier transform (STFT) gave the time-frequency-magnitude characteristic of continuous AE waveforms and useful information for evaluation of degradation of materials. In this study, the degradation of ceramic fiber mat during cyclic compression test and the effect of binder-addition were evaluated by this new system. STFT results clearly showed the classification of degradation of the mat; breakage of fibers was the main source in the early compression cycles and sporadic friction between fibers became the main source of AE in the later compression cycles. The effect of organic binder to prevent the degradation of the mat was also estimated. It was observed that the friction signal disappeared and the breakage signal weakened in the binder-added specimens.

Microstructure analysis of sintered Nd-Fe-B magnets improved by Tb-vapor sorption

Abstract: The surface treatment with Tb-vapor sorption improves the magnetic properties of small-sized magnets. Microstructure of the Tb-treated magnets was investigated by transmission electron microscopy (TEM). By applying the Tb-treatment, the diffusion of Tb through grain boundaries occurred even inside the magnets, and then a thin and continuous wetting-layer phase was formed at the boundaries between the Nd 2 Fe 14 B grains. The results suggest that the formation of the thin and continuous wetting-layer phase leads to the improvement in magnetic properties.

Comparison of Various Properties between Titanium-Tantalum Alloy and Pure Titanium for Biomedical Applications

Abstract: The mechanical properties, corrosion resistance and biocompatibility of the titanium-tantalum alloys together with pure titanium are comparatively studied for biomedical applications in this study. The experimental results confirm the previous theoretic investigation that tantalum has a potential to enhance the strength and reduce the elastic modulus of titanium alloys at the same time, and indicate that the titaniumtantalum alloys are more suitable than pure titanium for biomedical applications because of their lower elastic modulus, higher strength and enhanced corrosion resistance than pure titanium used as a standard metallic biomaterial, and the same excellent compatibility to pure titanium. [doi:10.2320/matertrans.48.380]

Production of Boron Carbide Reinforced 2024 Aluminum Matrix Composites by Mechanical Alloying

Abstract: Boron carbide particulates reinforced 2024 Aluminum matrix composites were fabricated by mechanical alloying–hot extrusion technology successfully. The morphology and microstructure of B4Cp/2024Al composite were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A clean interface of B4C between aluminum was obtained in this experiment, and matrix alloy revealed the typical microstructure of high energy milling with average grain size about 300 nm. Nanosized oxide and carbide formed after the composites subjected to high energy milling and hot consolidation process. The yield strength and Young’s modulus values were improved significantly over the monolithic 2024 alloy. [doi:10.2320/matertrans.48.990]

Production of Zr55Cu30Ni5Al10 Glassy Alloy Rod of 30 mm in Diameter by a Cap-Cast Technique

Abstract: used for the preparation of the master alloy. The purity of these metals; Zr(+Hf), Cu, Ni and Al were 99.99 mass%, 99.999 mass%, 99.99 mass% and 99.999 mass%, respectively. The alloy ingots were completely remelted, and cast into cylindrical rod samples with diameters from � 16 mm to � 30 mm by a modified cap-casting method, as shown in Fig. 1. The cap-cast technique was designed to obtain high cooling rate even at the upper part of cast specimen. The cast structure was examined by scanning electron microscopy (SEM), and the compositions of the quenched samples were determined with an electron probe microanalyzer (EPMA). The phase identification of the cast samples was performed by X-ray diffractometry. Oxygen concentration of the bulk glassy alloys was measured by a helium carrier fusioninfrared absorption. Microscopic cast structures were examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) using a JEOL 4000 FX. TEM samples were prepared by an electrolytic polishing machine using nitric methanol (30 vol% HNO3) at about 250 K.

Physical and Chemical Properties of Gas Hydrates: Theoretical Aspects of Energy Storage Application

Abstract: A model has been developed permitting to accurately predict on molecular level phase diagram of the clathrate hydrates. This model allows to take into account the influence of guest molecules on the host lattice and to extend the interval of temperatures and pressures of computed thermodynamic potentials and significantly improves known van der Waals and Platteeu theory. The theoretical study of phase equilibrium in gas–gas hydrate–ice Ih system for methane and xenon hydrates has been performed. The obtained results are in a good agreement with experimental data. A new interpretation of so-called self-preservation effect has been proposed. The self-preservation of gas hydrates can be connected with differences in thermal expansions of ice Ih and gas hydrates. This is confirmed by calculations performed for methane and mixed methane–ethane hydrates. [doi:10.2320/matertrans.48.704]

Free Volume Evolution in Metallic Glasses Subjected to Mechanical Deformation

Abstract: We define the Tumbull-Cohen free volume as the critical excess of the Voronoi volume of an atom less its core volume. Using molecular dynamics simulation we calculated the free volume change in two model binary metallic glasses undergoing tension and shear deformation. We show that the free volume change is an integral part of the deformation process; and the shear localization manifested as a shear band is directly related to the inhomogeneous distribution of the free volumes. Shear band formation may consist of two stages: the initial free volume production in the amorphous solids and the liquefaction of the regions with accumulated deformation strains. We show, for the first time, the formation of voids and the "vein" patterns on fracture surfaces at atomic scales; they are the combined result of the free volume change and loading and sample conditions.

Thermal Treatment of Municipal Sewage Sludge Aiming at Marketable P-Fertilisers

Abstract: Municipal sewage sludge is a carrier of nutrients – most important phosphorus (P) – but also contains organic pollutants and heavy metals. A two steps thermal treatment is suggested based on 1. mono-incineration of sewage sludge under destruction of organic pollutants and 2. thermochemical treatment of the resulting ashes to remove heavy metals and increase P-bioavailability. The targeted products are marketable Pfertilisers. The thermochemical treatment was investigated in a gas tight lab-scale rotary furnace. Seven sewage sludge ashes of different origin and composition and one residue from gasification of sewage sludge were mixed with a chlorine donor (e.g. MgCl2) and thermochemically treated under systematic variation of operational parameters. The distributions of the heavy metals between solid and gas phase were determined. The heavy metals concentrations of the treated ashes met the legislative limits in most cases. The products from thermochemical treatment are suited raw materials for P-fertiliser production. Relevant process parameters such as temperature, type and concentration of Cldonor and retention time were optimised for the thermochemical treatment step. [doi:10.2320/matertrans.MK200707]

Glass-Forming Ability and Mechanical Properties of the Ternary Cu-Zr-Al and Quaternary Cu-Zr-Al-Ag Bulk Metallic Glasses

Abstract: The effects of addition of Al and equivalent atomic ratio of Ag and Al on the glass-forming ability (GFA) of the Cu 50 Zr 50 alloy are investigated. It is found that the alloy with the highest GFA is the Cu 46 Zr 46 Al 8 alloy in ternary (Cu 50 Zr 50 ) 100-x Al x alloys, and the critical diameter is at least 8 mm. The simultaneous addition of Ag and Al is more effective to increase the glass-forming ability of the binary Cu 50 Zr 50 alloy. The critical diameter of a glassy rod is 12 mm for the Cu 42 Zr 42 Al 8 Ag 8 alloy. High stabilization of the supercooled liquid is the reason for high GFA of the Cu 46 Zr 46 Al 8 and Cu 42 Zr 42 Al 8 Ag 8 alloys. Both glassy alloys exhibited high fracture strength above 1960 MPa, but no distinct plastic strain is seen. There is no evident difference in the mechanical properties of the as-cast Cu 42 Zr 42 Al 8 Ag 8 glassy rods with different diameters.

Fabrication and Thermal Properties of Carbon Nanotube/Nickel Composite by Spark Plasma Sintering Method

Abstract: Multiwall carbon nanotube (MWNT) materials are attractive because they possess excellent thermal conductivity and mechanical properties. However, few reports exist that focus on improving the thermal conductivity of MWNT by combining it with a metal matrix. Thus to improve the thermal conductivity, a nickel-matrix composite with MWNT was prepared by slurry mixing process using ethanol as a solvent. Using spark plasma sintering (SPS), MWNT/Nickel nanocomposites were fabricated and the fabrication conditions were investigated. The sintered relative densities of the composites containing up to 5 vol% of MWNT were above 99%. The thermal and electrical behaviors of the MWNT/Nickel composites were determined using the laser flash and van der Pauw methods, respectively, and were found to be anisotropic. The thermal conductivity was found to increase by 10% for the composition with 3 vol% MWNT.

New TiZrCuPd Quaternary Bulk Glassy Alloys with Potential of Biomedical Applications

Abstract: In this paper, we have developed TiZrCuPd quaternary bulk glassy alloys which seem to be favorable for future application as biomaterials because of the absence of toxic elements such as Ni, Al and Be. A series of (TiZr) 50 (CuPd) 50 bulk glassy alloys exhibit high glass-forming ability (with critical diameters of 6 and 7 mm) and relatively large supercooled liquid region (AT",:) of over 50 K. This alloy system follows the three empirical rules for stabilization of supercooled liquid. The thermal stability of Ti 40 Zr 10 Cu 36 Pd 14 bulk glassy alloy was also examined in correlation with the origin for the high glass-forming ability.

Corrosion Behavior of a Ti-Based Bulk Metallic Glass and Its Crystalline Alloys

Abstract: The structure, thermal stability and corrosion behavior of the Ti40Zr10Cu36Pd14 bulk metallic glass and its crystalline alloys have been investigated in this paper. The results of potentiodynamic polarization measurements revealed that the Ti-based bulk metallic glass and its crystalline counterparts examined were spontaneously passivated by anodic polarization with the passive current density about 10 � 2 A/m 2 . The higher corrosion resistance for the Ti-based bulk metallic glass and partly crystalline alloys was attributed to stable and protective passive films enriched with titanium and zirconium. The Ti40Zr10Cu36Pd14 bulk metallic glass and its partial crystalline alloys produced recently without toxic elements are expected to be applied as biomaterials. [doi:10.2320/matertrans.MJ200713]

Deformation and Texture Evolution during High-Speed Rolling of AZ31 Magnesium Sheets

Abstract: Deformation of AZ31 sheets during high-speed rolling at various temperatures was investigated The thickness of 25 mm was reduced 60% by single-pass operation at a speed of 2000 m/min Textures, microstructures, mechanical properties and bendability of the sheets processed were examined In the sheets rolled at elevated temperature, equiaxed fine grains (<5 mm) having a basal texture with double peaks were formed around the center of the thickness The surface layer was sheared very severely by friction to form coarse grains having a welldeveloped basal texture with a single peak With increasing the rolling temperature, the grain size increases and the texture weakens slightly at the center The bendability of the sheet improves with increasing the rolling temperature The cold-rolled sheet having a deformation microstructure with shear bands and twins shows limited ductility [doi:102320/matertransL-MRA2007875] (Received March 6, 2007; Accepted June 13, 2007; Published July 19, 2007)

Morphology of Intermetallic Compounds in Al-Si-Fe Alloy and Its Control by Ultrasonic Vibration

Abstract: Iron impurity in aluminum alloys forms coarse needle-shaped intermetallic compounds during solidification and hampers the recycling process. To control the morphology of the material microstructure, an experiment was carried out where ultrasonic vibration was applied to the melt during solidification. Aluminum-Silicon-Iron alloys containing 4 mass% iron were melted and solidified. The primary crystals that formed from the melts were intermetallic compounds that were identified as Al3Fe, � -AlSiFe (Al7:4SiFe2) and � -AlSiFe (Al9Si2Fe2). The refinement of these intermetallic compounds was thought to occur with the application of ultrasonic vibration. Accurate results were obtained when the vibration was applied at the liquidus temperature. The liquidus temperatures of the Al-615Si-4Fe alloys were in the range of 945 to 955 K regardless of the silicon content and that of the Al-18Si-4Fe alloy was 977.2 K. Coarse plate-like intermetallic compounds formed in Al-6 mass%Si-4 mass%Fe and Al-12 mass%Si-4 mass%Fe alloys, which can be refined by the application of ultrasonic vibration on crossing the liquidus temperature on cooling. The coarse columnar structure of an Al18 mass%Si-4 mass%Fe alloy was modified to a fine grained structure. [doi:10.2320/matertrans.F-MRA2007874]

Improvement of Soft Magnetic Properties in (Fe0.85B0.15)100−xCux Melt-Spun Alloys

Abstract: The Cu content dependence of magnetic properties in annealed (Fe0:85B0:15)100� xCux alloys fabricated by melt-spinning was discussed. The value of Hc markedly decreases with increasing x between x ¼ 1:0 and 1.5, accompanied with significant reduction of crystalline grain size. The alloy with x ¼ 1:5 showed excellent magnetic properties such as a small Hc of about 7 A/m and a high Bs of more than 1.8 T. For the present alloy system, more than 1.0% addition of Cu is effective for the formation of nano-scale grains and for the improvement of the soft magnetic properties. [doi:10.2320/matertrans.MAW200730]